Physical Properties and Structure of Silica-Alumina-Europium Oxide Glasses

SiO₂–Al₂O3–Eu₂O₃ glasses were prepared for the composition 50siO₂·(50 – x )Al₂O_3·xEu₂O₃, and their density, sound velocity, and elastic modulus were measured. The chemical shift of the AIK a band emission spectra and the isomer shift of ¹⁵¹Eu by Mössbauer effect were obtained to determine the coordination states of Al³⁺ and Eu³⁺ ions in these glasses. It was found that the coordination number of Eu³⁺ ions was 12 and that the average coordination number of A1³⁺ ions was almost 5 in these glasses. By introducing Eu₂O₃, the packing of constituent ions was strongly enhanced and the elastic modulus increased in this system. The compositional dependence of the molar volume and elastic modulus were explained by these states of high coordination number for Eu³⁺ and low coordination number for Al³⁺ ions compared with those in the corresponding M₂O₃ crystals.